1. Field of the Invention
The present invention relates to a memory system such as a photo-disk memory and, particularly, to a memory system capable of high-speed reading even if the information recording area includes defective portions.
2. Description of the Prior Art
In the conventional magnetic disk memory, when the system has read out a defective area, e.g., a defective area due to a defect in the recording medium, the system always reads an alternative area which is intended to replace the defective area for compensating for the defect. The alternative area is generally located at a distance of several tracks, for example, from the defective area, and it takes a considerable time for positioning the reading head to the alternative area. Particularly, the photo-disk memory takes a positioning time about ten times longer than that of the magnetic disk memory due to the restrictions on the structure.